A259078 Heptagonal numbers (A000566) that are other heptagonal numbers divided by 2.

6426, 9875715583923, 15176968126834688342280, 23323916081375479417207129139097, 35844119643974208514403771705730853759974, 55085128439364942192092971212729781713850848998511, 84654649223375294035879228202426981713600292140166013136308

Offset: 1

Author

Colin Barker, Jun 18 2015

Keywords

• nonn
• easy

Examples

			6426 is in the sequence because 6426 is the 51st heptagonal number, and 2*6426 is the 72nd heptagonal number.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..109
• Index entries for linear recurrences with constant coefficients, signature (1536796803,-1536796803,1).

Crossrefs

Cf. A000566, A075528, A107736, A259079.

Programs

Mathematica

LinearRecurrence[{1536796803,-1536796803,1},{6426,9875715583923,15176968126834688342280},20] (* Harvey P. Dale, May 17 2018 *)

PARI

Vec(-189*x*(x^2+1372105*x+34)/((x-1)*(x^2-1536796802*x+1)) + O(x^20))

Formula

G.f.: -189*x*(x^2+1372105*x+34) / ((x-1)*(x^2-1536796802*x+1)).